This invention relates generally to a refrigeration circuit through which a refrigerant is circulated. A typical circuit comprises a compressor, an evaporator, an expansion valve, and a condenser as principal components, and an example of such a circuit is contained in an automobile air conditioning system. Such a system also comprises a desiccant assembly in the circuit to perform a desiccant function on the refrigerant. More specifically, this invention relates to a new and unique desiccant assembly and method.
In a typical refrigeration circuit, such as the type commonly used in automobile air conditioning systems, refrigerant is circulated through the circuit to produce cooling. The energy input to the circuit is via the compressor which is driven from the automobile's engine and which serves to create a source of pressurized liquid refrigerant which is allowed to expand through the expansion valve into the evaporator. In the evaporator the expanding refrigerant absorbs heat thereby producing cooling of a medium which is in heat transfer relationship with the evaporator. ln an automobile air conditioning system that medium is air. From the evaporator the refrigerant passes to a condenser where the heat absorbed in the evaporator is rejected. The heat rejection is to the outside environment in the described automobile air conditioning usage. The refrigerant is then drawn from the condenser by the compressor where it is again compressed and the cycle repeated.
It has been found desirable for the circuit to have a desiccant which acts on the refrigerant, basically for the purpose of collecting entrained moisture which may have been introduced into the refrigeration circuit for any of a number of possible reasons. In other words, the desiccant serves to prevent moisture from circulating through the circuit where its presence might give rise to undesired consequences.
Since the refrigeration circuit is a closed one, it is vital for the desiccant to be in an operative relationship with the refrigerant in a manner which maintains the closed nature of the circuit. The prevailing practice is for the desiccant to be contained in a desiccant assembly which comprises a cylindrical container having an inlet and an outlet for connecting it into the circuit. The desiccant is itself located within the container, and is typically contained in a bag which fits into the bottom of the cylindrical container. The construction of the container is such that refrigerant flow is directed through the desiccant so that the latter can perform its intended function of removing moisture from the refrigerant.
The prevailing practice in the fabrication of such desiccant assemblies comprises the container being formed of two separate parts, such two half shells or a base and a cap, joined together around a circular seam. The two parts are typically drawn or stamped. The various component parts of the desiccant assembly are assembled into the two container parts before the latter are seamed together.
This known process for fabricating the desiccant assembly has therefore comprised operations performed on two separate container parts, a subsequent assembly of various parts, and finally a joining of the two container parts together, such as by brazing in the case of aluminum or aluminum alloy, or by welding in the case of steel. The presence of the seam is a potential source for leakage, and from a practical manufacturing standpoint in mass production, reliability of this type of process has been shown to be poor. Significant reject and scrap rates have been tolerated as being a necessary consequence of the known manufacturing procedures. Even though a seam may visually appear satisfactory, there can be minute pin holes which form leak paths. The effectiveness of seaming procedures can be impaired because of the residual presence of materials used to facilitate the formation of one or both of the two container parts, i.e. the residual presence of lubricants or drawing compounds for instance when the parts are drawn or extruded.
The present invention is directed to a new and improved desiccant assembly which avoids the disadvantages associated with the prior manufacture of desiccant assemblies as just described. An important attribute of the invention is that it can significantly reduce the reject and scrap rates in the mass production of such desiccant assemblies. Moreover it is of a more efficient construction since it uses a single part to form the desiccant container rather than two separate parts seamed together.
The invention involves the application of friction spinning to the ends of seamless tube stock to form closed endwalls whereby the container comprises a single unitary body having a sidewall and integral endwalls. With the invention the continuous seam which was required in the prior manufacture is eliminated. The invention also involves the fabrication of various components and their subassembly to the one piece container at various stages of the fabrication process. Hence, related aspects of the invention involve the method of assembly.
The invention is adaptable to various packaging and geometrical configurations. In an automobile usage where the desiccant assembly may be located in the engine compartment, it is often necessary for the assembly to be in a limited space and for the inlet and outlet to be in particular geometric relationship to the container so that refrigerant lines can be connected to them. The invention is advantageously useful with different configurations, such as an external tube version and an internal tube version, examples of both of which will be subsequently hereinafter described.
In application of the invention to automobile air conditioning systems, important benefits accrue. The preferred embodiment of the present invention utilizes light-weight material which is consistent with the efforts of the automobile industry to make weight savings and fuel economy gains. It is also a better finished product suited to the quality improvement effort of the industry than is the prior multi-piece body construction.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.